Potentiometer



June 25, 1957 J. MONTGOMERY 2,797,286

POTENTIOMETER Filed April 13, 1955' 4 INVENTOR.

JAMES' L.. Momeomanv FIG. 3

V ATTYS.

POTENTIGMETER James L. Montgomery, Brookline, Mass.

Application April 13, 1955, Serial No. $891,217 4 Claims. (c1. 2tl156) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to potentiometers and more particularly to potentiometers that have a plurality of resistance elements.

Large quantities of potentiometers are used in military equipment, particularly in computing devices, and the design specifications for these potentiometers often require that physical dimensions be kept very small, however demanding highly accurate electrical performance. When a. group of potentiometers are driven from the same mechanical source, the potentiometers are often connected or stacked together mechanically. However, heretofore the physical connecting or stacking together of individual potentiometers resulted in a large assembled unit which occupied large volumes of space that was needed for other components.

The present invention overcomes the inherent disadvantage of stacking potentiometers by providing electrical resistance elements that occupy a minimum amount of space and are adaptable to be mounted or stacked together. The resistance elements of the present invention are composed of electrically insulated wire wound about annular rings or forms. The annular rings are preferably made of electrically insulating material, and each ring has a beveled edge on the inner diameter portion that engages with a brush element. Conducting disc members are spaced apart from the electrical resistance elements and support the brush assemblies and also serve as collector rings to conduct current. It is therefore a general object of the present invention to provide an improved type of potentiometer that can readily be stacked or connected mechanically to other similar potentiometers to provide an assembled unit that is not only economical in cost, but relatively small in size.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

Fig. 1 is a top plan view of an embodiment of the present invention;

Fig. 2 is a sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is 'a diagrammatic circuit showing the connection of a pair of resistance elements; and

Fig. 4 is a side view of a brush assembly.

Referring now to the drawing, wherein like reference characters designate like or corresponding parts throughout the several views there is shown an embodiment of the present invention that has four electrical resistance elements 11. Each resistance element 11 is comprised of an annular core 12 about which resistance wire 13, preferably of the varnish insulated type, is wound. Each annular core 12 has a beveled inner edge 14 that serves to provide a suitable surface for a brush element to make an 2,797,26 Patented June 25, 1957 electrical contact, and the portion of resistance wire 13 along the beveled inner edge 14 has the insulation removed therefrom.

Referring particularly to Fig. 2' of the drawing it can be seen that a first resistance element 11 is electrically insulated from a metallic top plate 15 by means of an insulating washer 16. A second resistance element 11 is mounted coaxially with the first resistance element 11, and a collecting ring 17 is interposed between the two resistance elements and electrically insulated therefrom by means of spacers 18. A brush assembly 1? contacts the collecting ring 17, and wipers 21, which are attached to the brush assembly 19, contact the resistance element 11 and make the electrical connection between the resistance element 11 and the conducting ring 17.

In Fig. 3 of the drawing there is shown the diagrammatic circuit of the two resistance units 11 and thecorresponding brush wipers 21.

Referring now to Figs. 2 and 4 of the drawing, it can be seen that the brush assembly 19 is composed of an insulating spacer 22 that fits about the shaft 23 and a pair of conducting washers 24 which has contacts 25 are secured to the insulating spacer by rivets or screws 26. The wipers 21 are also connected to the conducting washers 24 and the current flow will be through the wiper 21 to the conducting washer 24 and then through the contacts 25 to the collecting ring 17. The contacts 25, which for example can be rivet heads, also serve to rotatably support the brush assembly 19 on the collecting rings 17 The shaft 23, as illustrated in Fig. 2 of the drawing, has a square portion 27 and by providing a square hole in the insulating spacer 22 the brush assemblies 19 can readily be attached to the shaft 23 and no pins or set screws are needed. The end portions 28 are round and are rotatably mounted in bearings 29 that are seated in the top plate 15 and a bottom plate 31. It is apparent from the foregoing description that rotation of the shaft 23 will turn the brush assemblies 19 and thus change the amount of resistance to be placed in any suitable circuit.

The embodiment of the invention, as illustrated in Fig. 2 of the drawing, shows four resistance elements 11 wherein they are electrically connected together in pairs, as illustrated in Fig. 3 of the drawing. It should be understood, however, that there is no intention to so limit the present invention to an embodiment of four resistance elements, it being possible to use either a lesser or greater number merely by changing the length of the shaft 23 and the screws 32 that hold the units together.

Obviously many modifications and variations are possible in the light of the above teaching. 'For example the insulating washers 16 and spacers 18 could be eliminated by using resistance wire having a goo-d insulating coating and thus the size of the potentiometer could be reduced still further. Also a case could be placed between the top and bottom plates and around the outside of the resistance elements 11 to protect the potentiometer from damage. It is therefore to be understood that the invention may be practiced otherwise than as specifically described.

What is claimed is:

-1. A potentiometer comprising, a plurality of resistance elements comprised of annular cores each having an inner beveled surface and having resistance wire toroidally wound thereon, said resistance elements being mounted coaxially and grouped in pairs, a plurality of collecting rings mounted coaxially with said cores and in juxtaposition and interposed one each between each pair of resistance elements, a rotatable shaft mounted axially of said annular cores and said collecting rings, and a plurality of contacting means attached to said shaft whereby a separate contacting means slidably engages each said c01- contacting means includes an insulating spacer adaptable .to be fitted about said rotatable shaft, conducting Washers disposed on opposite sides of said insulating spacer and attached thereto, a wiper attached to each said conducting washer and adaptable for contacting separate resistance elements of a grouped pair, and contacts on each said conducting washer adaptable for slidably engaging said collecting ring.

3. A potentiometer comprising; a plurality of resistance elements having inner beveled surfaces and resistance wire toroidally wound thereon, said resistance elements being mounted coaxially and grouped in pairs; a plurality of collecting rings mounted coaxially with said resistance elements, one collecting ring being spaced between each pair of resistance elements; a rotatable shaft mounted axially of said resistance elements and said collecting rings; and a plurality of brush means carried by said rotatable shaft, one each being in contact with one of said collecting rings and the bevel surfaces of one of said pairs of resistance elements.

4. A potentiometer as set forth in claim 3 wherein said brush means includes an insulating spacer adaptable to be fitted about said rotatable shaft, conducting washers disposed on opposite sides of said insulating washer and attached thereto, a Wiper attached to each said conducting washer and adaptable for contacting separate resistance elements of a grouped pair, said wipers being electrically connected together, and contacts on each said conducting washer adaptable for slidably engaging one of said collecting rings.

References Cited in the file of this patent UNITED STATES PATENTS 2,431,749 Grant Dec; 2, 1947 2,492,727 Ballard Dec. 27, 1949 2,657,295 Barclay Oct. 27, 1953 

